Conventional light therapy comprises exposing a person, and especially the face to bright light, whereby the light is believed to be transported into the brain via the ocular route i.e. through the eyes. The drawback of conventional light therapy is that the amount of light required may be so high that delivering it via the ocular route may cause damage to the eye nerve, headache and other harmful side effects. Another drawback is that the recommended treatment time is at least half an hour, and preferably at least one hour, which limits a person's daily life. The person should also be very close to the light device to realize a therapeutic effect, preferably as close as 10-20 inches (30-50 cm), which makes administration cumbersome. Traditional light therapy lamps also must produce 2,500-10,000 lux, making these light units very high in energy consumption. Latel9-11y alternative routes for light therapy have been proposed. However, the knowledge of their effect is very limited and clinical evidence on treatment modalities like dosing or clinical intensities that would be needed for effective treatment have not been studied.
WO98/51372 discloses a method of resetting the circadian clock by applying non-solar photic stimulation of 15 to 150,000 lux, preferably 10,000 to 13,000 lux to any non-ocular region of the human body for 15 minutes to about 12 hours, preferably for 3 hours. Such treatment is hard to carry out without affecting normal activity. A method and device for directing optical radiation energy non-invasively at intra-cranial nerve tissue of a user through an external auditory canal is disclosed in WO2008/029001. The device is suggested for use e.g. in changing diurnal rhythm, in treating jetlag, sleep irregularity, seasonal affective disorder (SAD) etc. No details of treatment modalities are given. Another device for irradiating the inside of the auditory meatus with light is disclosed in JP2009034349.
The mode of action of light therapy is to an extent unknown. This is at least partly due to the fact that there is no easy way to measure the treatment effects induced or the very accurate amount of light delivered to treat a condition or to induce a desired treatment effect. A problem with light therapy is therefore that little is known about the dose of light needed to achieve a therapeutic effect without harmful side effects, as it has been impossible or difficult to administer an accurate dose. Lack of accurate administration has led to varying clinical trial results, and for example FDA being skeptical on approving light therapy devices. Another problem is that little is known about which routes of light treatment are effective. Still another problem is that the knowledge of physiological disorders responsive to light therapy is limited. The present invention provides a solution to overcome or at least alleviate the above problems and drawbacks.